Waste HCl acid solutions (usually 2-5M) containing toxic metals such as chromium, lead, copper, cadmium, etc. are classified as toxic waste. These solutions can come from a number of sources including the electroplating industry, the manufacture of printed circuit boards, the regeneration of cation exchange resins used in cleaning waste waters (including acidic mine drainage water), etc. The most common treatment practice for these toxic solutions in use is neutralization and precipitation which produces insoluble metal hydroxides; this method is costly because the neutralizing agent, usually sodium hydroxide, is relatively expensive. These solutions must then be replaced with new acid at additional expense. Another disadvantage is that the precipitated slurry consists of a mixture of metal hydroxides that has to be disposed of in designated toxic landfills. The disposal costs have been and will continue to rise due to tightening restrictions from the "Land Ban Act." Further, this practice does not stop the generators future liability should problems develop in the disposal facility.
In J. P. Faris, "Adsorption of the Elements from Hydrofluoric Acid by Anion Exchange," Anal. Chem., 32, pp. 520-522 (1960); S. F. Marsh et al., "Anion Exchange of 58 Elements in Hydrobromic acid and in Hydroiodic Acid.," Report LA-7084, August 1978 by Los Alamos Scientific Laboratory; and K. A. Kraus, et al., Proc. Intern. Conf. Peaceful Uses Atomic Energy, Geneva, 7, 113 (1956), all of which are incorporated herein by reference, there are described various methods for the removal of anionic metal complexes from many different solutions by adsorption on an anion exchange resin as well as techniques for the analytical separation of some of these metal species. Industrial techniques currently used to remove these anionic metal complexes from the resin do not separate them, thereby resulting in a solution still classified as toxic waste.